Your shop looks great Bob - love the floor!!! Mine is about the same size - 30'X36' and I can devote 2 bays to the bike if necessary... I'm guessing the weight of the 12" tire kit at just under 200 pounds... The larger tire kit, probably a bit more, but that is a guess, not a factual answer...
I run double darkside on my bike with a Yokohama Avid Envigor ZPS (run flat) on the rear and a Bridgestone Battlax BT-45 on the front... On my last tire change I had 17K on the Yoko with a bit of tread left on the edges but the center was worn flat, and the Battleax had 23K on it with a bit of tread left as well... I changed them both because I was leaving on a trip shortly after the change...
When running a run flat tire, TPMS is highly desirable and although my bike is equipped with the Honda TPMS system, I use a pre-production Tire Watch system that actually gives me pressure and temperature readouts using the bike's TPMS sensors... Unfortunately, this system never made it to market but works great... In any case, if your considering a run flat tire, think seriously about a TPMS system of some type...
I find the bike rides better with the car tire in the rear - a softer more supple ride, even the wife thinks so... It gets a bit twitchy on tar snakes and road seams but other than that handles well and is great in the rain too...
For what it's worth, I added a Traxxion 4.5 degree rake kit last year and the bike as a trike handles great - much less effort in the turns and the fatigue factor is greatly reduced... On 2 wheels the bike is still quite manageable, but there is a slight tendency to tuck in on the turns... So I now have the best of both worlds... The 4.5 degree rake kit works well on the Goldwing, but you would have to try it on the HD to see how it would be on 2 wheels, as I do not know the stock rake angle of the HD... As you may well know, these so called "rake kits" do not actually change rake angle, but rather actually change the trail angle, which can effect bike stability, so caution is advised if your considering doing this...
I will be following your install and will offer any help I can, even though yours is an HD and mine a Honda... I'm sure there are more similarities than differences...
Les